ELECTROLYTIC COLORING METHOD FOR ALUMINUM AND ALUMINUM ALLOY

PURPOSE:To efficiently form a uniform and beautiful colored layer on the surface Al by immersing an Al material subjected to an anodic oxidation treatment in an electrolytic coloring liquid and impressing a specific AC voltage thereto. CONSTITUTION:The Al or Al alloy material is anodized by an ordinary method using an acidic soln. such as sulfuric acid, oxalic acid or sulfamic acid to form an anodized film on the surface. The material is then immersed into the electrolytic coloring liquid which dissolves the sulfate, nitrate, phosphate, hydrochloride, oxalate, tartarate, etc. of metals such as Ni, Co, Cu, Mg, Fe, Mo, and Sn. The AC voltage of such a waveform as shown in the 1st time in which the AC voltage by the phase control of a thyristor as shown in the 3rd time is superposed on both the positive and negative voltages of a sinusoidal AC voltage (2nd time) is impressed to the Al material to electrolytically color said material. The control of the electrolytic voltage is executed with high accuracy and the beautiful and uniform electrolytic coloring is made possible.